Vapor generating and superheating unit



June 1966 J. H. AMMON ETAL 3,254,533

VAPOR GENERATING AND SUPERHEATING UNIT 1963 :5 Sheets-Sheet 1 Filed Feb. 28

INVENTORS Johannes H. Ammon BY Theodore S. Sprague ATTORNEY June 7, 1966 J. H. AMMON ETAL VAPOR GENERATING AND SUPERHEATING UNIT 3 Sheets-Sheet 2 Filed Feb. 28, 1963 R O T N E v m ATTORNEY June 7, 1966 J. H- AMMON ETAL VAPOR GENERATING AND SUPERHEATING UNIT Filed Feb. 28. 1963 5 Sheets-Sheet 5 INV EN TOR.

United States Patent F 3,254,633 VAPOR GENERATIhijG AND SUPERHEATING NIT Johannes H. Ammon, Akron, and Theodore S. Sprague, Hudson, Ohio, assignors to The Babcoek & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Feb. 28, 1963, Ser. No. 261,636 19 Claims. (Cl. 12232) This invention relates to a vapor generating and superheating unit and more particularly, to such a unit employing a heated liquid metal, such as sodium, as the heating medium.

At the present time steam generating plants employing sodium as the heat source, such as the Enrico Fermi Plant, are designed to superheat steam in the final flow stage of a once-through boiler, i.e., after the water has passed through the economizer and steam generating tube sections which comprise multiple parallel flow paths. Such an arrangement eliminates the need for a separate superheater unit. However, such units are limited in the maximum temperature of the superheated steam they deliver to about 900 F. for reasons of economics associated with the selection of alloys available for superheater tube manufacture. It would be possible to use stainless steel tubes throughout and thereby provide for higher superheated steam temperatures, but this type of construction would make the cost of the unit uneconomic. Another possibility would be to useferritic and austenitic tubing serially connected, ferritic for the low temperature portion of the unit and austenitic for the high temperature superheater portion. However, such a construction would place a bimetallic, dissimilar metals joint in the liquid metal flow path with consequent possibility of difficulty in eflecting and maintaining a satisfactory dissimilar metals welded joint. It is recognized, too, that the utmost in weld integrity is absolutely essential in order to minimize the danger attendant on leakage of water, thereby inhibiting the potentially violent liquid metalwater reaction.

One answer to this problem is to place the superheater in a separate unit when high temperature superheated steam is required. Such an arrangement is disclosed in the copending application, Serial No. 261,620, filed Feb. 28, 1963, in the names of Johannes H. Ammon, Paul B. Probert, John Schlichting and Theodore S. Sprague, and having the. same assignee as the present application. While such an arrangement overcomes the problem ofemploying two different and dissimilar metals in the same steam generating and superheating unit, considerable additional piping is required between the separate boiler and superheater as Well as an additional shell to house the superheater.

It is a primary object of the present invention to provide a once-through sodium heated steam generator capable of producing superheated steam at temperatures above 900 F. wherein both the boiler section and superheater section are disposed within the same vessel, and while employing different types of tubing do not require the welding together of dissimilar metals, e.g., ferritic and austenitic steels.

Another object of the present invention is to provide in the sodium flow path a by-pass around the superheater I Patented June 7, 1966 rately from the unit without'disturbing the other component.

Still another object of the invention is to provide an arrangement incorporating a steam reheat superheater within the same vessel as the boiler and superheater sections.

Additional objects of the invention are to provide a helically coiled tube arrangement wherein the tubes may be of substantially equal length though of diiferent coil diameters, to afiord a pressure vessel construction which will permit the separate removal of the superheater and boiler sections of the unit, and to supply a construction in which heated liquid metal will be prevented from contacting the walls of the pressure vessel.

Therefore, the present invention provides a vapor generating and superheating unit comprising a vertically arranged pressure vessel incorporating a cylindrical container open at its upper end, and which is spaced inwardly from and in coaxial alignment with the vessel so that an annular space is provided between the two. Within the container, and in coaxial alignment with it, is a sleeve having its lower end spaced above the bottom of the container. Disposed inwardly of the sleeve is a vertically extending conduit member situated concentrically about the vertical axis of the pressure vessel.

The positioning of the conduit member and the sleeve provides an annular passageway which contains a bank of vertically extending helically coiled vapor generating tubes disposed subjacent to a similar helically coiled vertically extending bank of superheater tubes.

A heating liquid, such as liquid sodium, is supplied to the container by inlet means through the vessel shell and opening into the container below its top. The level of the heating liquid is maintained below the top of the container and above the top of the superheater tubes. Within the conduit member are a pair of by-pass valves for routing the heating liquid around the superheater tubes or the boiler tubes.

In order that the superheater tubes and boiler tubes may be separately removed from the pressure vessel, the

inlet and outlet chambers for these tubes are located in removable segments of the pressure vessel located above the top of the container. Further, inlet and outlet sections of the boiler tubes form a basket-like arrangement with the superheater tubes positioned within it so that the superheater tube bank can be removed without interfering with the adjacent boiler tubes.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of'this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described preferred embodiments of the invention.

' Of the drawings:

FIG. 1 is a vertical sectional view of a vapor generating and superheating unit embodying the present invention; 1

FIG. 2 is a top view of the unit shown in FIG. 1;

FIG. 3 is a vertical view partly in section of another embodiment of the present invention incorporating a reheater into the vapor generating and superheating unit;

FIG. 4 is a greatly enlarged detail view of the encircled section of FIG. 1; and

FIG. 5 is a view taken along line 5-5 in FIG. 4.

The vapor generating and superheating unit illustrated in FIG. 1 has certain basic features which derive from the copending application Serial No. 802,880, filed March 30, 1959, now Patent No. 3,112,735, inventors John Schlichting and Theodore S. Sprague, having the same assignee as the present invention.

In the present arrangement a vapor generating and superheating unit is disposed Within a vertically extending cylindrical pressure vessel 12. The vessel 12 is made up of a main member 14 having a curved lower head 16, a relatively short spool member 18 attached to the upper end of the main body member and an upper head member 20 attached to the top of the spool member and forming theupper closure for the vessel. Flanges 22, 24 are located on the upper end of the main body member 14 and on the lower end of the spool member 18, respectively, for bolt connecting these two sections together. Similarly the upper end of the spool member 18 and the lower end of the upper head member 20 have flanges 26, 28, respectively, which are also bolt connected.

Within the pressure vessel 12 is a vertically extending container arranged in coaxial relationship with the vessel and extending from a point closely spaced above the lower head 16 to a plane coincident with the closure joint between the flanges 22, 24. The container is open at its upper end 32 and is spaced about its vertical periphery closely from the pressure vessel forming therewith an annular space 34. Spaced lugs 36 are located in the annular space 34 between the container and the vessel at various levels for maintaining the proper space relationship between the two elements.

Within the container and closely spaced from its inner surface is a vertically arranged concentrically disposed sleeve 38 which acts as a shroud. At its lower end the sleeve is spaced above the bottom of the container while its upper end terminates just above the top of the container. The sleeve has a smaller diameter for its lower half 40 than for its upper half 42 thereby providing a ring-shaped channel 44 of greater width about the lower part of the sleeve than about its upper part. A number of vertically spaced rings 45 are positioned in the channel 44 for separating the sleeve and the container. These rings 45 are attached to the sleeve but are not connected to the container. The rings are slotted (not shown) to provide openings for tubes to pass through them.

Disposed inwardly from the sleeve is a centrally arranged vertically positioned conduit member 46 which extends from the bottom of the container 30 to the lower end of the upper head member 20. In combination with the sleeve 38 the conduit member 46 forms an annular passageway 46A.

In the upper head member 26 is a heating liquid inlet 47 which extends into the interior of the pressure vessel and connects to a ring-shaped distribution header 48. Extending downwardly from the header 48 are a plurality of heating liquid outlets 50 which depend into the container so that the discharge openings 52 are located a substantial distance below the open top of the container. Each of the heating liquid outlets 50 has walls which diverge from the header 48 to the discharge openings 52 thereby decreasing the velocity of the heating liquid as it enters the container and reducing the possibility of turbulence at that point. The outlets 50 are uniformly distributed within the container so that they can evenly deliver the heating liquid to the horizontal cross section of the container. Within the container 30 between its open top 32 and the discharge openings 52 from the heating liquid outlets 50 is a heating liquid level 53. Centrally located in the lower end of the container is a heating liquid outlet duct 52A which is connected to the container wall and arranged to form a thermal sleeve construction with the adjacent wall of the lower head 16 of the pressure vessel.

In the spool member 18 four cylindrically-shaped headers 54 are formed having a tube sheet 56 coextensive with the wall of the spool member and a removable header closure plate 58 closing the opposite end of the header. Two of these headers 54 act as inlet chambers 60 for the vaporizable fluid in the unit, and the other two been vaporized.

In view of the various tubes disposed within the vessel arrows have been provided to indicate the direction of flow of the water as it passes through the unit and the location of the tubes. Initially, vaporizable fluid downcomer tubes 64 pass from the inlet chambers 60 downwardly through the annular channel 44. At the lower end of the sleeve these downcomer tubes are bent radially inward and then upward into a bank of helically coiled vapor generating tubes 66 which are located within the annular passageway 46A. For a more complete explanation of the manner in which the helically coiled tubes are disposed in the reactor, reference is made to the copending application of John Schlichting, Serial No. 249,- 152, filed Jan. 3, 1963, having the same assignee as the present application.. As explained in the copending application, by selectively arranging the helically coiled tubes, each tube irrespective of its coil diameter will be of substantially equal length for its path through the bank of vapor generating tubes. The upper end of the bank of vapor generating tubes 66 coincides with the top of the lower portion 40 of the sleeve 38. At the top of the bank the riser tubes 67 are again bent radially outward to the interior surface of the upper portion 42 of the sleeve 38 and then extend upwardly into the tube sheets 56 of the outlet chambers 62.

From each of the outlet chambers 62 a vapor connection pipe 68 extends upwardly to a vertically positioned vapor inlet chamber 70 located in the upper head member 20 of the pressure vessel. There are two of these vapor inlet chambers 78 formed of cylindricallyshaped walls attached by means of a thermal sleeve arrangement 72 to the upper head member. The lower end of the chambers are closed by tube sheets 74 and the opposed upper ends have cover plates 76 closing off the inlet chambers. Constructed similarly to the inlet chambers and also positioned in the upper head member are a pair of superheated vapor outlet chambers 78'.

Vapor downcomer tubes 80 are connected to the tube sheet 74 and extend vertically downward into the container 20 being closely spaced about the interior of the upper half 42 of the sleeve 38 immediately inward of the riser tubes 67 which extend from the bank of vapor enerating tubes to the outlet chambers 62. The vapor inlet tubes 88 extend downwardly to a point just above the bank of vapor generating tubes 66 and then extend radially inward being formed into a bank of helically coiled superheating tubes 82 situated in the annular passageway 46A above the bank of vapor generating tubes 66. The height of the bank of su perheating tubes is substantially less than that of the bank of vapor generating tubes and extends upwardly to a plane spaced subjacent to the discharge opening 52 from the heating liquid outlets 56. After steam is superheated within the bank of superhe-at'ing tubes 32 outlet tubes 84 extend upwardly to the superheated steam outlet chambers 78 and from thence the superheated steam is delivered to a point of use (not shown).

The conduit member 46 is divided into an upper section 86 and a lower section 87. The upper section 86 is suspended from the upper 'head member 20 by hanger bars 88 and terminates between the banks of vapor generating and superheating tubes. At its lower end the upper section fits into a recess 89 formed in the inner surface of a main support member 99, see FIG. 4, form.- ing a sliding joint therewith. At the upper end of the lower section 87, it is attached to the main support member 90, while at its lower end, it fits into a recess 92 in the lower end of the container at the heating liquid outlet connection 52A.

In the upper section 8-6 of the conduit member are a pair of vertically spaced cylindrically-shaped sliding valves 94A, 94B. Valve 94A is located immediately above the bank of superheater tubes, and valve 94B is located immediately below the same bank. These two Valves are connected to a vertically positioned shaft 96 which extends upwardly through the upper member 20 of the pressure vessel and is located within a blowout nozzle 98. Attached to the upper end of the shaft is a rack and pinion gear 100 by which the valves 94A and 94B may be positioned between the :full open and full closed positions.

At the lower end of the lower section 87 of the conduit member 46 is a heating liquid outlet sliding valve 102 which is disposed at the entrance to the heating liquid outlet 52A. At the upper end of the lower section 92 is another sliding valve 104 which is disposed immediately above the top of the bank of vapor generating tubes. Both of the valves 102 and 104 are connected to a vertically disposed shaft 106 which extends upwardly within the shaft 96 and is connected to another part of the rack and pinion gear 100 for moving these valves into the desired position.

v The valves 94A, 94B are used to by-pass some portion of the heating fluid flowing through the container about the superheating tubes 82 so that the vapor temperature from the superheater tubes may be regulated. Since these valves can be moved into a number of positions between their fully opened and closed dispositions, it is possible to achieve a wide'range of outlet temperatures for the superheated vapor issuing from the bank of superheated tubes 82. As shown in FIGS. 1 and '4 the sliding valves are in a lower or fully closed position. By operating the rack and pinion gear 100 the shaft 96 is moved upwardly simultaneously lifting the sliding valves 94A, 94B and opening slots 95A, 9513 in the conduit member an equal amount so that a certain portion of the heating liquid can bypass the superheater tubes. To prevent heating liquid, which has 'oy-passed the superheater tubes, from continuing downwardly through the conduit member 46, a baflie 107, see FIGS. 4 and 5 for detail, is located within the conduit member at the bottom of the valve 94B for directing the flow of the lay-passed heating liquid outwardly through valve 94B and for preventing its continued passage downwardly through the conduit member. 108 hinged about their lower faces to the upper end of the valve 104. Normally these leaves will be in a down position 108A, however, if a gas pressure builds up in the lower end of the vessel, the gas can escape up through the conduit member by forcing the leaves up into an open position 108B. Once the gas escapes, the leaves will reseat closing the conduit member against any downward flow of heating liquid.

Valves 102 and 104 are employed for by-passiug the heating liquid about the vapor generating tubes. Ordinarily all of the heating liquid passing through the container flows over the vapor generating tubes. However, if some emergency arises which prevents the Vaporizable fluid passing through the vapor generating tubes from carrying off the heat from the heating liquid, then thevalve 104 is opened and valve 102 is closed so that the This baflie is comprised of six leaves temperature materials which might otherwise be required. Additionally, the inert gas also acts to pressurize the heating liquid for maintaining the position of its level and further, it prevents any air from entering the vessel and contacting the heating liquid which might cause serious damage, depending on the nature of the heating liquid.

The inner surfaces of the spool member 18 and the upper head member 20 are covered with an internal insulation 112 which protects the inner surfaces of both of these structures from the high inert gas temperatures in the vessel.

connection pipes 68 which extend between the vapor outlet chamber 62 and the vapor inlet chamber 70. After heating liquid bypasses the bank of vapor generating tubes completely flowing downwardly through the lower portion 87 of the conduit member and out through the heating liquid outlet.

Located in the upper head is an inlet connection (not shown) which delivers inert gas into the pressure vessel. The inert gas fills the pressure vessel in the space above the level of the heating liquid within the container and the vapor connection pipes 68 have been severed, the inner shaft 106 disconnected from its drive mechanism and the bolts removed from the flanges 26 and 28, the bank of superheater tubes can be removed as a unit with the upper heat member and the upper portion of the conduit member and 'hollow shaft 96. It will be noted that the superheater tubes along with the connections to and from their inlet and outlet chambers are located radially inward from any of the downcomer and riser connections to the vapor generating tubes so that there is no interference when they are removed from the pressure vessel. The superheater tubes are supported from the upper head member 20 by means of a combination of radially extending horizontal supports 114 which extend between the wall of the upper head member and the hanger bars 88. Depending from these members 114 are a plurality of hanger bars 116 which in turn carry a ring support 118 located immediately above the bank of superheater tubes.

Tube support bars (not shown) hang downwardly from the ring support 118 to hold the helically coiled tubes in the superheater bank. Reference may be had to the previously mentioned copending application, Serial No. 802,880, now Patent No. 3,112,735, and Serial No. 249,- 152, which has the same assignee as the present application for an illustration of the type of tube support referred to.

Once the superheater tubes are removed from the vessel, the vapor generating tubes can in turn be removed by disconnecting the spool member 18 from the main body of the pressure vessel. Since the vapor generating tubes are attached to the inlet and outlet chambers lo,- cated in the spool member they can be removed from the vessel as a unit with the sleeve 38 and the lower section 87 of the conduit member which is attached to the main support member 90. The vapor generating tubes are supported in the same manner as described above and more fully illustrated in the referenced copending appli cations.

It is also desirable to combine one or more reheaters in the same vessel with the superheater and vapor generating tubes, in such an arrangement as is shown in FIG. 3. The general arrangement in FIG. 3 is similar to that shown in FIG. 1, and for that reason, it is not considered that a detail description or illustration is required.

In FIG. 3 a pressure vessel 120 comprises a main body member 122, a lower and an upper spool member 124 and 126 respectively arranged above the main body member with an upper head member 128 forming the closure for the vessel. Within the pressure vessel is a container 130 open at its upper end and spaced inwardly from the vessel wall. Within the container and extending above its open end are a series of concentrically arranged spaced sleeves 132, 134 and 136 similar in construction to that shown in FIG. 1. Sleeve 132 is connected by means of a lug 138 to the lower spool member 124 while sleeves 134 and 136 are connected to the upper spool member 126 by means of lugs 140, 142, respectively.

Within the container a helically coiled bank of vapor generating tubes 144 disposed below a similarly coiled bank of reheater tubes 146. Within the sleeve 136 above the container is a bank of helically coiled superheater tubes 148. These tubes are connected at their inlet and outlet ends into chambers 156, 152, 154 disposed respectively in the spool member 124 for the vapor generating tubes, in the spool member 126 for the reheater tubes and in the upper head member 128 for the superheater tubes.

The heating liquid feed system 156 is somewhat different from that shown in FIG. 1 since it is divided to provide flow control of the heating liquid over both the superheater and reheater tubes. Heating liquid inlet line 153 is divided by a baflie 159 into a superheater feed line 164 and a reheater feed line 162, each line having its own valves 164, 166, respectively. From feed line 160 the heating liquid enters an annular-shaped distribution header 168 which delivers the heating liquid into a number of heating liquid outlets 170 similar to those described in FIG. 1. A heating liquid level 172 is formed within the sleeve 136 above both the bank of superheater tubes and the discharge opening 174 from the outlets 170.

correspondingly, the heating liquid in the reheater feed line 162 branches off from the inlet line 158 and enters a ring-shaped distribution header 176. From the header 176 the heating liquid flows downwardly through the outlets 178 which are positioned in the space between the sleeves 134 and 136 for supplying the heating liquid to the bank of reheater tubes 146 which are located in the lower enlarged spac 180 between the same sleeve.

In this manner the banks of superheater and reheater tubes each receive a separate supply of heating liquid so that individual control of the superheat and reheat temperatures may be attained. At the lower end of the sleeve 136 the two separate streams of heating liquid flow together and then pass downwardly over the bank of vapor generating tubes and then on out of the container 130 through outlet 182.

For ease in tracing the path of the vaporizable fluid through the pressure vessel arrows have been placed on the various inlet and outlet lines. vaporizable fluid feed enters the downcomer tube 184 from the inlet chamber 150 (I) and passes downwardly in the space between the container 130 and the sleeve 132. Below the bottom of sleeve 132 the tubes are bent into the bank of vapor generating tubes 144. Vapor outlet tubes 186 extend from the top of the vapor generating tubes 144 in the space between sleeves 132 and 134 and are connected to the outlet chamber 150 (O).

From the outlet chamber 150 (O) the vapor passes through the pipe 188 to the inlet chamber 154 (I) of the superheater tubes. Downcomer tubes 196 run from the inlet chamber 154 (I) within the sleeve 136 to the lower end of the bank of superheater tubes 148 to which they are connected. At the top of the superheater tubes riser tubes 192 extend upwardly to the superheated steam outlet chamber 154 (O), and from this chamber the superheated steam is delivered to a point of use (not shown).

After the superheated vapor is utilized in a unit such as a turbine it could then be returned to the pressure vessel 120 to be reheated for additional use in the turbine. Vapor to be reheated enters the unit through the inlet chamber 152 (I) and is carried from there to the bottom of the reheater tubes 148 by means of inlet tubes 194 which are located between sleeves 134 and 136. From the top of the reheater tubes outlet pipes 196 carry the reheated vapor upwardly between th sleeves 134 and 136 and then into the outlet chamber 152 (I) from where it is transported to a point of use (not shown).

As described in FIG. 1 the various banks of tubes and their inlet and outlet connections are disposed in what may be characterized as a basket arrangement, one within the other, so that they may be removed individually from the vessel without one interfering with the other. The only connection between the various banks is the vapor pipe 188 running between the outlet chamber 150 (0) from the vapor generating tubes to the inlet chamber 154 (I) to the superheating tubes. Additionally, they are, in effect, connected by means of the flanges and the various members which make up the overall pressure vessel. By breaking the connection between the flanges and the vapor pipe 188 the various banks of tubes may be sequentially removed from the vessel in this fashion; first, Withthe upper head member 128, the bank of superheater tubes 148; second, with the upper spool member 126, the bank of reheater tubes 146 and the sleeves 134 and 136; and third, with the lower spool member 124, the bank of vapor generating tubes 144 and the sleeve 132. This leaves the main body of the pressure vessel and the container undisturbed.

In addition, the pressure vessel contains a conduit member 198 which provides the inner boundary for an annular passageway 26%) within which the banks of vapor generating 144 and superheating tubes 148 are located. As in the arrangement shown in FIG. 1 the conduit member 198 contains a pair of valves 202 for by-passing the heating liquid about the superheater tubes and a pair of valves 204 for by-passing the heating liquid about the vapor generating tubes. Further, the conduit member contains a baflle 206 which prevents the heating liquid, which has by-passed the superheater tubes, from flowing down through the conduit member and out of the vessel. This arrangement of valves and battle is operated in the same manner as that described for the similar arrangement shown in FIG. 1.

It will be noted that the inlet and outlet chambers for the various tube arrangements each has a covered plate through which access may be gained to the tube ends for any maintenance which may be required upon them.

In the arrangement described the preferred heating liquid would be sodium and the vaporizable fluid would be water. It is possible, however, that other metals having similar characteristics to that of sodium may be used as the heating liquid while the vaporizable fluid is not necessarily restricted to water.

In the units embodying the present invention it is possible due to the arrangement of the tube to avoid the use of any bimetallic joints between the vapor generating and superheating tubes to utilize the most economical metals in view of the temperatures to be developed.

Therefore, this invention provides a unit which may be simply assembled and dismantled and which permits the most economical use of tube metals in view of the temperature conditions desired from the unit.

While in accordance with the provisions of the statutes we have illustrated and described herein the best forms and modes of operation of the invention now known to us,

. those skilled in the art will understand that changes may be made in the forms of the apparatus disclosed without departing from the spirit of the invention covered by our claims, and that certain features of our-invention may sometimes be used to advantage without a corresponding use of other features.

What is claimed is:

1. vapor generating and superheating unit wherein a heating liquid passes in indirect heat transfer relationship with a vaporizable fluid comprising:

A. a vertically arranged pressure vessel comprising a number of mechanically connected serially removable sections forming its upper portion and including a removable head member and at least one separately removable circumferentially extending wall member,

B. an upwardly extending container open at its upper end and spaced within and forming an annular space with said. pressure vessel,

C. heating liquid inlet. means attached to one of the removable sections of said vessel and having-the discharge end thereof located within and below the open end of said container, and a heating liquid level formed within and below the open end of said container,

D. a vertically extending bank of vapor generating tubes arranged within said container below the level of the heating liquid,

E. a vertically extending bank of superheater tubes disposed within said container below the level of the heating liquid and in vertical alignment with said bank of vapor generating tubes,

F. wall means attached to one of said removable sections and forming an inlet chamber and an outlet chamber for said vapor generating tubes, and

G. wall means attached to a different one of said removable sections and forming an inlet chamber and an outlet chamber for said superheater tubes, whereby the banks of vapor generating and superheater tubes may be individually removed from the vessel with the wall means forming their respective inlet and outlet chambers and the removable section to which the wall means are attached.

2. A vapor generating and superheating unit as set forth in claim 1 wherein a bank of vertically extending reheater tubes are disposed in said container below the liquid level therein in vertical alignment with said bank of vapor generating tubes.

3. A vapor generating and superheating unit as set forth in claim 2 wherein said bank of reheater tubes is located above said bank of vapor generating tubes and below said bank of superheating tubes.

4. A vapor generating and superheating unit as set forth in claim 1 wherein a vertically disposed sleeve is located within and spaced from said container with its lower end situated above the bottom of the container, and a centrally arranged vertically extending conduit member is positioned within said pressure vessel and spaced inwardly from said sleeve forming an annular passageway therebetween within said container, said annular passageway containing said banks of vapor generating and superheating tubes.

5. A vapor generating and superheating unit as set forth in claim 1 wherein heating liquid by-pass means are disposed within said container whereby the heating liquid flowing therethrough may be regulably and selectively routed about said vapor generating and superheating tubes.

6. A vapor generating and superheating unit as set forth in claim 5 wherein said heating liquid by-pass means comprises a pair of vertically spaced valves positioned in said conduit member with one valve located immediately above and the other located immediately below said bank of superheating tubes, and means connected to said valves for selectively arranging them as a unit between fully closed and fully opened positions for regulably routing said heating liquid about said bank of superheater tubes to control the final temperature to which the vapor passing therethrough is superheated.

7. A vapor generating and superheating unit as set forth in'claim 6 wherein said heating liquid by-pass means comprises a second pair of vertically spaced valves positioned in said conduit member with one valve disposed immediately above said bank .of vapor generating tubes and the other valve disposed below said bank of vapor generating tubes, and means connected to said valves for selectively operating them as a unit whereby one valve is always in a fully closed position and the other valve is always in a fully opened position for alternatively discharging the heating liquid from said container and for routing the heating liquid about said bank of vapor generating tubes.

8. A vapor generating and superheating unit as set forth in claim 7 wherein said bundle of vapor generating tubes is disposed below said bundle of superheating tubes, and said inlet and outlet chambers for said vapor generating tubes are attached to said removable wall member and the inlet and outlet chambers for said superheating tubes are attached to said removable head member whereby said removable head member and wall-member may be removed from the main body member of the a pressure vessel and said superheating tubes and said vapor generating tubes may be removed respectively with them.

9. A vapor generating and superheating unit as set forth in claim 8 wherein inlet tubes extend downwardly from the inlet chamber in said wall member through the space between said container and sleeve to the lower end of said vapor generating tubes and vapor outlet tubes extend upwardly within the sleeve from the top end of the bank of vapor generating tubes to the outlet chamber in said wall member.

10. A vapor generating and superheating unit as set forth in claim 9 where-in a vapor pipe is connected to and extends between the vapor outlet chamber in said wall member and the superheating inlet chamber in said head member.

11. A vapor generating and superheating unit as set forth in claim 10 wherein inlet .pipes extend downwardly from said superheater inlet chamber within said sleeve to the lower end of said bundle of superheater tubes and cally coiled in a multiplicity of vertically extending circular rows having varying diameters and arranged so that each tube may be of substantially equal length throughout its bank.

13. A vapor generating and superheating unit as set forth in claim 1 wherein the interior surfaces of said removable head member and wall member have an insulation covering for protecting the inner surface of said memllaers from the high temperatures existing within said vesse 14. A vapor generating and superheating unit as set forth in claim 13 wherein a'gas connection is disposed in the removable head member of said pressure vessel for providing inert gas to the. space between said pressure vessel and container and above the heating liquid level in said container for containing any pressure surge result ing from the interaction, caused by leakage, between the heating liquid and the fluid being vaporized.

15. A vapor generating and superheating unit as set forth in claim 14 wherein tube support means are positioned immediately'above both said bank of vapor generating tubes and said bank of superheater tubes for separately supporting each bank so that they may be separately removed from the vessel.

16. A vapor generating and superheating unit as set forth in claim 15 wherein the heating liquid is sodium and the vaporizable fluid is water.

17. A' vapor generating and superheating unit as set forth in claim 6 wherein a bafile is disposed within said conduit member below the lower of said valves which by-pass the heating liquid around said bank of superheating tubes for preventing the heating liquid from continuing to flow downwardly through said conduit mem-' in counter-flow relationship with the vaporizable fluid passing through the banks of tubes therein.

19. A vapor generating and superheating unit wherein F. wall means attached to a different one of said rea heating fluid passes in indirect heat transfer relationship movable sections and positioned above and in comwith a vaporizable fluid comprising: munication with said bank of superheating tubes A. a vertically arranged pressure vessel comprising a for forming an inlet chamber and an outlet chamber number of mechanically connected serially remova- 5 for the superheating tubes said removable sections ble sections forming its upper portion and including in the same vertical relationship as the banks of a removable head member and at least one separately removable circumferentially extending wall member,

tubes with which they are in communication whereby the removable sections with their attached inlet and outlet chambers and bank of tubes may be in- B. heating fluid inlet means attached to one of the 10 dividually removed from the Pressure Vesselremovable sections for delivering a heating fluid into said vessel, C. a vertically extending bank of vapor generating References Cited by the Examiner UNITED STATES PATENTS tubes arranged within said vessel, 2,865,827 12/1958 Dwyer 12232 D. a vertically extending bank of superheating t bes 3,018,764 1/1962 Huet 12234 disposed within said vessel in vertical alignment with FOREIGN PATENTS said bank of vapor generating tubes, E. wall means attached to one of said removable sec 803382 10/1958 Great Bntam' tions and positioned above and in communication 20 with said bank of vapor generating tubes for forming an inlet chamber and an outlet chamber for the vapor generating tubes, and

FREDERICK L. MATTESON, 1a., Primary Examiner.

KENNETH W. SPRAGUE, Examiner.

PERCY L. PATRICK, Assistant Examiner. 

1. A VAPOR GENERATING AND SUPERHEATING UNIT WHEREIN A HEATING LIQUID PASSES IN INDIRECT HEAT TRANSFER RELATIONSHIP WITH A VAPORIZABLE FLUID COMPRISING: A. A VERTICALLY ARRANGED PRESSURE VESSEL COMPRISING A NUMBER OF MECHANICALLY CONNECTED SERIALLY REMOVABLE SECTIONS FORMING ITS UPPER PORTION AND INCLUDING A REMOVABLE HEAD MEMBER AND AT LEAST ONE SEPARATELY REMOVABLE CIRCUMFERENTIALLY EXTENDING WALL MEMBER, B. AN UPWARDLY EXTENDING CONTAINER OPEN AT ITS UPPER END AND SPACED WITHIN AND FORMING AN ANNULAR SPACE WITH SAID PRESSURE VESSEL, C. HEATING LIQUID INLET MEANS ATTACHED TO ONE OF THE REMOVABLE SECTIONS OF SAID VESSEL AND HAVING THE DISCHARGE END THEREOF LOCATED WITHIN AND BELOW THE OPEN END OF SAID CONTAINER, AND A HEATING LIQUID LEVEL FORMED WITHIN SAID BELOW THE OPEN END OF SAID CONTAINER, D. A VERTICALLY EXTENDING BANK OF VAPOR GENERATING TUBES ARRANGED WITHIN SAID CONTAINER BELOW THE LEVEL OF THE HEATING LIQUID, E. A VERTICALLY EXTENDING BANK OF SUPERHEATER TUBES DISPOSED WITHIN SAID CONTAINER BELOW THE LEVEL OF THE HEATING LIQUID AND IN VERTICAL ALIGNMENT WITH SAID BANK OF VAPOR GENERATING TUBES, F. WALL MEANS ATTACHED TO ONE OF SAID REMOVABLE SECTIONS AND FORMING AN INLET CHAMBER AND AN OUTLET CHAMBER FOR SAID VAPOR GENERATING TUBES, AND G. WILL MEANS ATTACHED TO A DIFFERENT ONE OF SAID REMOVABLE SECTIONS AND FORMING AN INLET CHAMBER AND AN OUTLET CHAMBER FOR SAID SUPERHEATER TUBES, WHEREBY THE BANKS OF VAPOR GENERATING AND SUPERHEATER TUBES MAY BE INDIVIDUALLY REMOVED FROM THE VESSEL WITH THE WALL MEANS FORMING THEIR REPSECTIVE INLET AND OUTLET CHAMBERS AND THE REMOVABLE SECTION TO WHICH THE WALL MEANS ARE ATTACHED. 